The Oscar-winning actor Philip Seymour Hoffman was found dead on Sunday morning in his New York apartment, after a suspected drug overdose. He was 46.

Hoffman’s body was discovered by a friend in the bathroom of his apartment in Bethune Street, in the West Village neighbourhood of Manhattan, around 11.15am ET.

In a statement, Hoffman's family said: “We are devastated by the loss of our beloved Phil and appreciate the outpouring of love and support we have received from everyone. This is a tragic and sudden loss and we ask that you respect our privacy during this time of grieving. Please keep Phil in your thoughts and prayers."

A law enforcement source told the Guardian the New York police department had opened a “DOA” (“Dead on arrival”) investigation and was investigating a possible drug overdose. The NYPD's inquiry will take place alongside Office of the Chief Medical Examiner, which is determining the precise cause of death.

A small group of people stood behind a police barricade at the end of Hoffman's street in Manhattan's West Village late on Sunday afternoon.

"He was one of the people you associate with New York as opposed to California," said Aaron Kinney, 32, who lives in Manhattan and had travelled to the area to pay his respects with friend Sharlota Kay.

"He was a true actor. Not Hollywood style, not pompous," Kay said.

Kristen Diventi, 27, lives a few streets from the apartment. A friend sent her an email to tell her about the death. She came to "see if it was true".

"We lost another great one," she said. "I'm still not over James Gandolfini. Another true New Yorker.

"I think it's tragic. Heroin is taking way too many lives and hopefully this will wake everybody up who has an addiction."

Hoffman, who was from Fairport, New York, was one of America’s most loved actors. In 2005, he won the Academy Award for best actor for his leading role in Capote, a film based on the life of the novelist Truman Capote.

He is survived by his three children and their mother, Mimi O’Donnell, a costume designer with whom he had been in a long-term relationship.

“Saddened by Philip Seymour Hoffman's tragic and untimely passing,” the New York mayor, Bill de Blasio, said on Twitter. “Today New York mourns the loss of one of stage and screen's greats.”

Ellen DeGeneres, the comedian and talk show host, tweeted: “Philip Seymour Hoffman was a brilliant, talented man. The news this morning is shocking and sad. My heart goes out to his loved ones.”

DeGeneres will host next month’s Oscars, which are likely to be dominated by Hoffman’s death.

The precise circumstances of Hoffman’s death were not known. He was last seen publicly 10 days ago, at the Sundance film-festival in Utah, when he gave a number of interviews to journalists about his role in John Slattery’s directorial debut, God’s Pocket.

Hoffman had admitted to suffering from drug and alcohol addiction problems after graduating from theatre school in 1989. He had spoken of checking himself into a rehabilitation clinic but until recently was believed to have been clean for 23 years. In a 2011 interview with the Guardian, Hoffman said his alcohol and drug problem had been "pretty bad" and expressed his fear that it might one day return.

"I know, deep down, I still look at the idea of drinking with the same ferocity that I did back then. It's still pretty tangible," he said. Referring to his younger days, Hoffman added: "I had no interest in drinking in moderation. And I still don't. Just because all that time's passed doesn't mean maybe it was just a phase."

It is understood that Hoffman was last seen alive on Saturday night, around 8pm. The friend who discovered Hoffman unconscious in his bathroom on Sunday is believed to be a playwright and a long-time associate.

Multiple media reports, citing law enforcement officials, said Hoffman was found with a needle in his arm and that a substance believed to be heroin was in the apartment. Those reports could not be independently verified, however officials confirmed they believed his death was drug-related.

Hoffman's death was first reported in the Wall Street Journal, shortly after 1pm on Sunday. An NYPD car was photographed on the road outside the apartment – with officers standing by the apartment-block door. By 2pm, satellite TV trucks arrived outside the property, followed by a growing throng of mourners, some of them neighbours who described Hoffman as an unassuming member of the community.

An ambulance arrived shortly after 3pm.

Hoffman came to prominence as an actor in the early 1990s. Despite his widely-acclaimed role as the protagonist in Capote, he mostly worked in supporting roles. He was nonetheless widely regarded as one of the best actors of his generation.

He received his third Academy Award nomination in the best supporting actor category in 2012, in recognition of his performance in The Master.